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Message-Id: <1427900864-13891-1-git-send-email-hannes@stressinduktion.org>
Date: Wed, 1 Apr 2015 17:07:44 +0200
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: netdev@...r.kernel.org
Cc: "hannes@...essinduktion.org" <hannes@...essinduktion.org>,
Jiri Pirko <jiri@...nulli.us>
Subject: [PATCH net-next] ipv6: protect skb->sk accesses from recursive dereference inside the stack
From: "hannes@...essinduktion.org" <hannes@...essinduktion.org>
We should not consult skb->sk for output decisions in xmit recursion
levels > 0 in the stack. Otherwise local socket settings could influence
the result of e.g. tunnel encapsulation process.
ipv6 does not conform with this in three places:
1) ip6_fragment: we do consult ipv6_npinfo for frag_size
2) sk_mc_loop in ipv6 uses skb->sk and checks if we should
loop the packet back to the local socket
3) ip6_skb_dst_mtu could query the settings from the user socket and
force a wrong MTU
Furthermore:
In sk_mc_loop we could potentially land in WARN_ON(1) if we use a
PF_PACKET socket ontop of an IPv6-backed vxlan device.
Reuse xmit_recursion as we are currently only interested in protecting
tunnel devices.
Cc: Jiri Pirko <jiri@...nulli.us>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
Jiri tried to fix this bug by passing down the tunnel sock pointer.
Currently there should be no difference in behaviour with this patch.
http://patchwork.ozlabs.org/patch/380404/
http://patchwork.ozlabs.org/patch/380406/
http://patchwork.ozlabs.org/patch/380405/
In case we do need more specific fragmentation setup semantics we would
need to go with Jiri's approach. Currently we don't care about sk_mc_loop
for kernel sockets, so it is easy to just shut them up. Other options
are safe as well.
Please review carefully!
include/linux/netdevice.h | 6 ++++++
include/net/ip.h | 16 ----------------
include/net/ip6_route.h | 3 ++-
include/net/sock.h | 2 ++
net/core/dev.c | 4 +++-
net/core/sock.c | 19 +++++++++++++++++++
net/ipv6/ip6_output.c | 3 ++-
7 files changed, 34 insertions(+), 19 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 967bb4c..1064075 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2176,6 +2176,12 @@ void netdev_freemem(struct net_device *dev);
void synchronize_net(void);
int init_dummy_netdev(struct net_device *dev);
+DECLARE_PER_CPU(int, xmit_recursion);
+static inline int dev_recursion_level(void)
+{
+ return this_cpu_read(xmit_recursion);
+}
+
struct net_device *dev_get_by_index(struct net *net, int ifindex);
struct net_device *__dev_get_by_index(struct net *net, int ifindex);
struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);
diff --git a/include/net/ip.h b/include/net/ip.h
index d0808a3..69cd9cb 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -455,22 +455,6 @@ static __inline__ void inet_reset_saddr(struct sock *sk)
#endif
-static inline int sk_mc_loop(struct sock *sk)
-{
- if (!sk)
- return 1;
- switch (sk->sk_family) {
- case AF_INET:
- return inet_sk(sk)->mc_loop;
-#if IS_ENABLED(CONFIG_IPV6)
- case AF_INET6:
- return inet6_sk(sk)->mc_loop;
-#endif
- }
- WARN_ON(1);
- return 1;
-}
-
bool ip_call_ra_chain(struct sk_buff *skb);
/*
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 1d09b46..eda131d 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -174,7 +174,8 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
{
- struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+ struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
+ inet6_sk(skb->sk) : NULL;
return (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) ?
skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
diff --git a/include/net/sock.h b/include/net/sock.h
index 3f9b8ce..bd6f523 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1762,6 +1762,8 @@ struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie);
struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie);
+bool sk_mc_loop(struct sock *sk);
+
static inline bool sk_can_gso(const struct sock *sk)
{
return net_gso_ok(sk->sk_route_caps, sk->sk_gso_type);
diff --git a/net/core/dev.c b/net/core/dev.c
index 65492b0..08c0df9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2849,7 +2849,9 @@ static void skb_update_prio(struct sk_buff *skb)
#define skb_update_prio(skb)
#endif
-static DEFINE_PER_CPU(int, xmit_recursion);
+DEFINE_PER_CPU(int, xmit_recursion);
+EXPORT_SYMBOL(xmit_recursion);
+
#define RECURSION_LIMIT 10
/**
diff --git a/net/core/sock.c b/net/core/sock.c
index 119ae46..654e38a 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -653,6 +653,25 @@ static inline void sock_valbool_flag(struct sock *sk, int bit, int valbool)
sock_reset_flag(sk, bit);
}
+bool sk_mc_loop(struct sock *sk)
+{
+ if (dev_recursion_level())
+ return false;
+ if (!sk)
+ return true;
+ switch (sk->sk_family) {
+ case AF_INET:
+ return inet_sk(sk)->mc_loop;
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+ return inet6_sk(sk)->mc_loop;
+#endif
+ }
+ WARN_ON(1);
+ return true;
+}
+EXPORT_SYMBOL(sk_mc_loop);
+
/*
* This is meant for all protocols to use and covers goings on
* at the socket level. Everything here is generic.
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 84c58da..654f245 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -542,7 +542,8 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
{
struct sk_buff *frag;
struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
- struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+ struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
+ inet6_sk(skb->sk) : NULL;
struct ipv6hdr *tmp_hdr;
struct frag_hdr *fh;
unsigned int mtu, hlen, left, len;
--
2.1.0
--
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